<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>clearfix</title>
    <style>
        .box1{
            width:200px;
            height:200px;
            background-color:deeppink;
        }
        /* .box1::before{
            content:'';
            display:table;
        } */
        .box2{
            width:100px;
            height:100px;
            background-color: chartreuse;
            margin-top:100px;/*外边距重叠问题*/
        }

        /*直接可以背下来：clearfix可以同时解决高度塌陷和外边距重叠问题，当你再遇到这些问题时，直接使用clearfix来解决*/
        .clearfix::before,
        .clearfix::after{
            /*外边距重叠*/
            content:'';
            /*显示为一个表格*/
            display:table;
            /*高度塌陷*/
            clear:both;
        }

    </style>
</head>
<body>
    <div class="box1 clearfix">
        <div class="box2"></div>
    </div>

    
</body>
</html>